Ardesia is an usefull software for use your desktop as a Sketchpad. You can write, markup and erase, also, of course, you can use your desktop as normal desktop.
According to website, no new version since 2012, latest issue reported was 2015.Just tested in Ubuntu 18.04, doesn't work. Was also reported to not work in Ubuntu 14.04.
Ardesia vs Epic Pen opinions
because it helps me make my videos better.
Draw, record and have fun!